1. Field of the Invention
The present invention relates to a position measurement system which measures a distance to a light source by detecting an optical ring image formed from light originating from the light source, by spherical aberration of a lens.
2. Description of the Preferred Embodiments
In relation to a technique for measuring a three-dimensional position of a light source with high accuracy and high resolving power, various methods have hitherto been proposed. For instance, one method employs a camera having an auto-focusing mechanism. This method requires two cameras, which in turn adds to cost, or suffers a problem of difficulty in speeding up measurement because focusing action involves consumption of time. Another method utilizes a laser beam as a light interference method. This technique uses a laser beam, and hence entails a problem of a necessity for safety precautions, or the like. Moreover, the so-called light interference lens method presents a problem of computation for measuring a position from an interference pattern being complicated.
JP-A-2004-212328 has been proposed as a measure for solving these problems. This technique is to measure the position of a light source (a point source of light) by utilization of spherical aberration of the lens. Specifically, according to this method, the light emitted from the light source; e.g., an LED, is converted into an optical ring image (a light-concentrated area) by spherical aberration of the lens. This optical ring image is detected by a CCD sensor, and the position of the light source is measured on the basis of detection information about the thus-detected optical ring image (e.g., the diameter of the optical ring).